I've lived in the US and Australia. Something I've noticed in these threads is Australians/europeans not actually understanding that it's a different system not merely topping up someone's wage as an extra, in the US it is core to the industry model, unlike Australia/europe.
The menu items are cheaper in the US as the restaraunt pays below minimum wage to the worker (like $3 an hour) who is expected to earn the remainder of their wages through tips. If there is a shortfall, the restaraunt will top up the base wage to the minimum wage, which isnt a living wage.
The expectation is that the customer rewards good service, creating a meritocracy for the servers and filtering out shit servers or motivating them to improve. Further, if you are a repeat customer, the staff will remember who tips well and will take care of them, for example if you are at a crowded bar, they will go out of their way to serve you your drinks before others who arent regs and/or dont tip.
By going there, not tipping but taking the benefit of the cheaper prices, you are fucking over the staff, causing them to go from having a living wage to a non living wage and exploited. A lot of these servers are students, young parents, single parents, marginalised groups, etc. So by not tipping good service, in the US, you are being a piece of shit.
In Australia, where the prices are higher, the staff makes a living wage. It makes little sense to tip then. Frankly, the service in Australia is shit however, in my experience, but at least less people are exploited